Farmers are rarely expected to be experts in hydrology and drainage. However, they need to at least learn the basics to keep their fields from flooding and to control erosion around irrigation systems and farm roads. Drainage systems, both surface and subsurface designs, are essential for carrying away irrigation and fertigation water that is high in nutrients, chemicals, and other contaminants. Proper slope and volume capacity creates a clear path for all waste water to flow away from the fields and to holding ponds or other processing areas. Agriculture draining systems play all of the following roles and more on large scale commercial farms relying on irrigation or natural rainfall.
Protecting Local Waterways
Agricultural runoff water is too high in many organic compounds and dissolved minerals to safely blend into local waterways. Yet due to the need for a steady water supply, many crop fields are located directly adjacent to creeks, rivers, ponds, and other natural bodies of water. Drainage systems intercept this runoff after it drains from the fields and before it can reach the nearest natural source of water. Nitrogen in particular from crop fertilizers is damaging to local waterways due to the encouragement of expansive algae blooms. The algae absorbs all of the oxygen in the water, resulting in mass fish die-offs and damage to the native plants holding the banks together.
Controlling Water Loss
Agricultural drainage systems also manage water loss in areas where every drop is needed for irrigation. Water diverted from the fields into holding tanks or ponds is easily recycled and applied to the fields. If the runoff is too high in salt or fertilizer content, it’s easily diluted with a smaller amount of fresh water to work around watering restrictions and high water costs. Liners are especially important for this reason since they prevent water loss through seepage. Unlined ditches and canals will lose much of their water to seepage as the runoff travels across the soil. Of course, any holding ponds built for pumping the water back to irrigation equipment will also need flexible liners for the same reason.
Modulating Soil Moisture Levels
Subsurface drainage systems are significantly more complicated than surface systems. However, they’re well worth the effort to lower the water table in an area where the soil remains wet for months at a time. High levels of seasonal rainfall go beyond supplying a crop’s needs and saturate the soil to the point of flooding. Crops quickly die off when water stands for more than a day or two because the roots can’t absorb oxygen from the gaps between the soil. Buried perforated pipes, commonly known as drain tiles, soak up as much subsurface water as possible and redirect it to lined ditches and canals to carry it away from fields and roads where it’s not needed.
Allowing for Water Reuse
An advanced agricultural drainage system gives you complete control over where the excess irrigation water ends up after each application. For most farms, reusing the runoff directly is the best way to manage it. If more advanced treatments and processing services are available, the leftover irrigation water may become clean enough to use for watering livestock, washing harvested crops, or producing secondary products. Only a liner drainage system will keep the irrigation runoff clean enough for these kinds of reuse opportunities after further processing.
Preventing Erosion
By directing excess rainfall and irrigation runoff into lined and stabilized drainage ditches and canals, it’s possible to limited soil erosion as much as possible. With conventionally plowed fields losing up to 1 mm of soil per year due to the combination of wind and water erosion, it’s essential to limit this loss as much as possible. Erosion does more than just remove valuable soil volume from your fields. It also destabilizes roads, hillsides, and the banks of ponds and irrigation canals. Designing and building a simple drainage system is the best way to control erosion across your entire acreage.
Monitoring Water Quality
Lined drainage canals and pits give you a great opportunity for sampling runoff water for testing. Many farmers test their field runoff to see how much of their fertilizer is being absorbed and how much is wasted. Runoff water can also reveal salinity problems in the soil and the presence of contaminants from nearby manufacturing facilities or livestock operations. Since drainage systems tend to mix and accumulate water from a wide range of fields, you may want to add sampling pits higher up in the system to ensure you can pinpoint which areas are contributing to a problem.
Agricultural drainage systems can vary in complexity from a simple set of ditches to a complicated set of interconnected canals, ponds, and treatment zones. No matter what kind of drainage system you plan to add to your farm, make sure you’re using a liner that can take the challenge. Turn to BTL Liners for multi-layered RPE liners that won’t react with fertilizers or chemical contaminants, even after daily exposure.
